It’s not often that chemists find a quick, simple and cheap method for making things using widely available ingredients, but researchers have done just that: They’ve created elegant little capsules and coatings in water simply by mixing iron and a compound from plants called tannic acid. The soft coatings form on their own around whatever else is in the water — glass beads, bacteria, gold nanoparticles and more. Just changing the solution’s pH can prompts the coatings to disassemble.